Voltage references, such as bandgap voltage references, are widely used in various analog and digital integrated circuit functions, e.g., analog-to-digital and digital-to-analog conversion. The operation of a bandgap voltage reference relies upon the voltage difference between two diodes, often operated at the same current and having different junction areas, that is used to generate a proportional to absolute temperature (PTAT) current in a first resistor. This current is used to generate a voltage in a second resistor. This voltage in turn is added to the voltage of one of the diodes (or a third one, in some implementations). If the ratio between the first and second resistors is chosen properly, the first order effects of the temperature dependency of the diodes and the PTAT current will cancel out. The resulting voltage is about 1.2-1.3 volts, depending on the particular technology used, and is close to the theoretical bandgap of silicon at 0 K.
However, the diodes used in the bandgap voltage reference generate noise that is introduced into circuits coupled to the bandgap reference (voltage+noise). The diodes and support circuits used in the bandgap voltage reference require a lot of integrated circuit die real estate and consume a fair amount of power during operation thereof. Initial output voltage distribution from the bandgap voltage reference during startup is not stable until a certain time passes. The voltage from the bandgap reference also varies with temperature.